Changes of Nodular Size and Its Risk Factors in Iodine-Sufficient Area: a Retrospective Cohort Analysis of 7753 Thyroid Nodules

Background and Objectives: Iodine is known to be an important factor in the occurrence of goiter, and SouthKorea is a region with sufficient iodine supplementation. In this regard, we checked the size change of thyroidnodules found by health check-up in Koreans and examined which risk factors influence the size change. Materialsand Methods: A total 7753 subjects who underwent thyroid sonography two or more times were included. Wedefined that there was a change in the size of the nodule when the difference in diameter identified in the lastultrasound was more than 3 mm. Results: Thyroid nodules were decreased in 895 subjects (11.5%) and increasedin 1041 subjects (13.5%). The rate of increased nodule was on an increasing trend according to the duration(annual percent change 2.6%, p＜0.001). In contrast, the rate of decreased nodule was unchanged. Predictivefactors related to decrease of the nodule size were young age, male sex, larger initial nodule size and thyroiditis. Similarly, young age, larger initial nodule size and diffuse parenchymal abnormality were significant predictivefactors for increased nodules. However, diffuse parenchymal abnormality was not a predictive factor when weanalyzed only thyroid nodules larger than 1 cm. Conclusion: In our study, 11.5-13.5% of benign thyroid noduleswere increased or decreased during median 27 months of follow-up in iodine sufficient condition. Young age,larger initial size and diffuse parenchymal abnormality were common predictive factor affecting both the increaseand decrease of thyroid nodules. KCI Citation Count: 0